Multi-mode power trains with direct-drive lock-up

ABSTRACT

A multi-mode power train and multi-mode vehicle are disclosed. A power-conversion device is in communication with an engine via a direct mechanical power-transfer connection extending from the engine to the power-conversion device. A continuously variable power source (CVP) is in communication with the power conversion device via an intermediate power-transfer connection. A lock-up device with first and second engagement states is provided between the engine and the power-conversion device or the CVP. With the lock-up device in the first engagement state, mechanical power from the engine is converted by the power-conversion device for use by the CVP, with the CVP using the converted power to provide mechanical power to a power-output connection. With the lock-up device in the second engagement state, the engine transmits mechanical power through the lock-up device to the power-output connection.

CROSS-REFERENCE TO RELATED APPLICATION(S)

Not applicable.

STATEMENT OF FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

FIELD OF THE DISCLOSURE

This disclosure relates to transmissions, including transmissions foroperation of work vehicles in different powered modes.

BACKGROUND OF THE DISCLOSURE

It may be useful, in a variety of settings, to utilize both atraditional engine (e.g., an internal combustion engine) and ancontinuously variable power source (e.g., an electric or hydrostaticmotor) to provide useful power. For example, in a vehicle or otherpowered platform having both an engine and a continuously variable powersource, a portion of the engine power may be diverted to drive apower-conversion device (e.g., a hydraulic pump or an electric machineacting as a generator), which may in turn drive the continuouslyvariable power source (e.g., a hydraulic motor or another electricmachine acting as a motor). The output of the continuously variablepower source may then be utilized to execute useful operations (e.g., todrive a vehicle or operate machinery associated with the vehicle).

In certain applications, a vehicle or other platform may be configuredto operate in various different powered modes. For example, a vehiclemay be configured to operate in a direct-drive mode, in which power isutilized from the engine only, as well as in other modes in which acontinuously variable power source (e.g., an electric or hydraulicmotor, which may be powered, indirectly, by the engine) is utilized tovarying degrees.

SUMMARY OF THE DISCLOSURE

A multi-mode power train and multi-mode vehicle are disclosed. Accordingto one aspect of the disclosure, a power-conversion device may be incommunication with an engine via a direct mechanical power-transferconnection extending from the engine to the power-conversion device. Acontinuously variable power source (“CVP”) may be in communication withthe power conversion device via an intermediate power-transferconnection. A lock-up device with first and second engagement states maybe provided between the engine and the power-conversion device or theCVP. With the lock-up device in the first engagement state, mechanicalpower from the engine may be converted by the power-conversion devicefor use by the CVP, with the CVP thereby providing mechanical power to apower-output connection. With the lock-up device in the secondengagement state, the engine may transmit mechanical power through thelock-up device to the power-output connection.

In certain embodiments, the power-conversion device may include ahydraulic pump or an electric generator and the CVP may include,respectively, a hydraulic motor or an electric motor.

In certain embodiments, the engine, the power-conversion device, thelock-up device and the CVP may be arranged in series, with respect tothe path of power transmission. The lock-up device may include a clutchdevice between the power-conversion device and the CVP, the clutchdevice being integrated with a rotor of the CVP.

In certain embodiments, the lock-up device may include a clutch assemblyand a gear. With the lock-up device in the first engagement state or thesecond engagement state, the CVP or the engine, respectively, maytransmit power to the power-output connection via the clutch assemblyand the gear.

In certain embodiments, the lock-up device may include a first clutchdevice and a first gear, with a second clutch device and a second gearbeing included between the CVP and the power-output connection. With thelock-up device in the first engagement state and the second clutchengaging the second gear, the CVP may transmit mechanical power to thepower-output connection via the second clutch and the second gear. Withthe lock-up device in the second engagement state, the engine maytransmit mechanical power to the power-output connection via the firstclutch device and the first gear.

In certain embodiments, an energy storage device may in communicationwith the CVP and the power-conversion device. In a first mode, theenergy storage device may receive energy for storage from at least oneof the power-conversion device and the CVP. In a second mode, the energystorage device may provide stored energy from the energy storage deviceto the CVP.

The details of one or more implementations are set forth in theaccompanying drawings and the description below. Other features andadvantages will become apparent from the description, the drawings, andthe claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of an example vehicle with a multi-mode powertrain;

FIG. 2 is a schematic view of certain components included in an examplemulti-mode power train of the vehicle of FIG. 1;

FIG. 3 is a schematic view of certain components included in anotherexample multi-mode power train of the vehicle of FIG. 1;

FIG. 4 is a schematic view of certain components included in yet anotherexample multi-mode power train of the vehicle of FIG. 1;

FIG. 5 is a schematic view of certain components included in stillanother example multi-mode power train of the vehicle of FIG. 1; and

FIG. 6 is a graphical representation of example vehicle tractive effortand vehicle wheel speeds for various modes of operation of themulti-mode power train of FIG. 5.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

The following describes one or more example embodiments of the disclosedmulti-mode power trains, as shown in the accompanying figures of thedrawings described briefly above. Various modifications to the exampleembodiments may be contemplated by one of skill in the art.

As noted above, in work vehicles or other platforms, a portion ofmechanical power from an engine (including, potentially, all of theengine power) may sometimes be converted to another form in order todrive a continuously variable power source (“CVP”). For example, anengine may be utilized to drive an electric generator or a hydraulicpump, with the resulting electrical or hydraulic power being utilized,respectively, to drive an associated electric or hydraulic motor.

In this light, it will be understood that a vehicle (or other platform)may sometimes be capable of operation in a variety of powered modes. Forexample, in a direct-drive or purely mechanical mode, mechanical powermay be directly transmitted from the engine to a power-output connection(e.g., a transmission output shaft, differential drive shaft, powertake-off shaft, and so on). In contrast, in a different mode (or modes),the same (or a different) power-output connection may alternatively (oradditionally) receive mechanical power from the CVP. For example, in apurely electric (or hydraulic) mode, all of the mechanical power fromthe engine may be routed for conversion to electrical (or hydraulic)power in order to drive an electric (or hydraulic) motor. The motor maythen act as a sole power source for operation of the vehicle (or variousvehicle components). Despite the inherent efficiency losses in theconversion of engine power for the CVP in such a latter mode (or modes),the characteristics of electric or hydraulic motors (or other CVPs) mayprovide for improved performance of a vehicle (or other platform) duringcertain operations. Accordingly, in certain settings, it may be usefulto provide a system that allows for efficient transition betweendirect-drive and other modes (e.g., purely electric or purely hydraulicmodes).

In certain embodiments, for example, an engine (e.g., an internalcombustion engine) may provide mechanical power to a power train. Thepower train may also include a power-conversion device, such as anelectric generator or a hydraulic pump, and an associated CVP, such asan electric or hydraulic motor. The engine may provide mechanical powerto the power-conversion device, which may convert the received power toa form that may be used by the CVP (e.g., electricity for an electricmotor, or hydraulic pressure or flow for a hydraulic motor). In certainembodiments, the engine may provide mechanical power to thepower-conversion device over a direct mechanical power-transferconnection that extends from the power source to the power-conversiondevice. For example, the engine may provide mechanical power to thepower-conversion device over various mechanical shafts and gears,without the use of a torque converter or other fluid coupling. (As usedherein, “direct mechanical” power transmission may include transmissionof mechanical power by direct physical connection, through variousintegrally formed parts, or via various intervening mechanical elementssuch as a gear set to modify rotational speeds. In contrast, forexample, power transmission using a torque converter or other fluidcoupling may not be considered a “direct mechanical” transmission.)

Continuing, a lock-up device may be provided as part of the power train,in order to allow for transition between direct-drive and other poweredmodes (e.g., purely electric or hydraulic modes). A lock-up device maybe configured in various ways, and may be located in various placeswithin the power train. In certain embodiments, a lock-up device mayinclude a clutch device (or similar mechanism) located between theengine and either of the power-conversion device or the CVP. (As usedherein, “between” may refer to a location with respect to a flow ofpower, rather than an actual physical location. As such, for example, aclutch device may be viewed as located “between” an engine and apower-conversion device if power is routed, at least in part, from theengine through the clutch device in order to reach the power-conversiondevice.)

In certain embodiments, when a clutch device (or another lock-up device)is in a first engagement state, it may provide a direct-drive (i.e.,direct mechanical) connection between the engine and various downstreamcomponents of the power train. In this way, for example, the clutchdevice may allow for direct mechanical transmission of power from theengine to a downstream power-output connection (e.g., an output shaft ofa power-shift transmission, a differential drive shaft, a power take-offshaft, and so on), and, correspondingly, for direct-drive operation ofthe vehicle.

Continuing, when the clutch device (or another lock-up device) is in asecond engagement state, the direct mechanical connection between theengine and the power-output connection may be may severed, and analternative path provided for power transmission between the CVP and thepower-output connection. In this way, through the transition of theclutch device (or other lock-up device) between different engagementstates, a power train may be transitioned between a direct-drive mode(i.e., a mode in which power is provided to an output connection solelyfrom the engine) and a CVP mode (i.e., a mode in which power is providedto the output connection solely from the CVP). (It will be understoodthat even in the CVP mode, the engine may still provide power to theoutput connection indirectly, as the engine may continue to providepower, via the power-conversion device, to drive the CVP.)

Among other benefits, such a multi-mode power train may usefully allowfor a combination of control and efficiency, without the need for atorque converter or other fluid coupling between the engine and variousother components of the power train. For example, it will be understoodthat a torque-converter (or other similar mechanisms) may provide forrelatively effective torque control (e.g., via actuation of a throttlepedal). However, it will also be understood that a torque-converter maylead to relative low system efficiency, particularly athigh-load/low-speed applications. For example, in a vehicle applyinglarge draw-bar force with low or zero wheel speed (e.g., when aheavily-loaded vehicle is starting from a stop or otherwise trying toshift a heavy, stationary load), large amounts of energy may be wastedby thermal/fluidic dissipation within a torque-converter. In contrast, aCVP (e.g., an electric motor) may provide relatively high, andrelatively loss-free, torque at low wheel speeds. However, a CVP mayintroduce inefficiencies because of the need to convert mechanical powerfrom an engine to a form compatible with the CVP (e.g., electricalpower), so overall system efficiency may be increased by switching fromCVP mode to direct-drive mode for certain operations. In this light, byproviding for a system which may easily switch between a CVP mode (e.g.,for operations at low vehicle speeds) and a direct-drive mechanical mode(e.g., for operations at higher vehicle speeds), high system efficiencyand useful torque control may be attained without requiring the use of atorque converter (and the losses inherent thereto). Additionally, such asystem may allow for optimization of an included CVP (and thepower-conversion device) to a relatively narrow speed range (e.g.,through selection of a high torque/low speed CVP), thereby allowing forpotentially significant cost savings.

As will become apparent from the discussion herein, the disclosed powertrain configurations may be used advantageously in a variety of settingsand with a variety of machinery. For example, referring now to FIG. 1,the disclosed system may be included in power train 12 of work vehicle10. In FIG. 1, work vehicle 10 is depicted as a tractor. It will beunderstood, however, that other configurations may be possible,including configuration of work vehicle 10 as a different kind oftractor, an articulated dump truck, a front-end or back-hoe loader, alog skidder or other forestry equipment, a motor grader, or one ofvarious other work vehicles. It will also be understood that thedisclosed power train configurations may be used in various non-workvehicles and non-vehicle applications (e.g., fixed-location poweredmachinery).

Referring now to FIG. 2, an example configuration of multi-mode powertrain 12 is provided. As depicted in FIG. 2, various components of anexample of power train 12 are arranged in series. It will be understood,however, that other configurations may be possible, and that certaincomponents depicted (or not depicted) in FIG. 2 may not be (or may be)included in other embodiments. (As discussed above regarding the use of“between,” “series” may be utilized herein with respect to a flow ofpower, rather than an actual physical location. As such, for example,various devices may be viewed as oriented “in series” if power is routedsequentially from one to another, rather than being routedsimultaneously to a plurality of the devices.) Engine 14 may beconnected by mechanical power-transfer connection 16 (e.g., a rotatingshaft, various gears, and so on), but not by a torque converter or otherfluid coupling, to power-conversion device 18 and, in certainembodiments, also to device 20 (e.g., a hydraulic charge pump).Power-conversion device 18 may convert the received mechanical power toan alternative form (e.g., electrical or hydraulic power) and maytransmit the converted power over connection 36 to CVP 26 or energystorage device 34 (e.g., a battery assembly or hydraulic accumulator).In certain embodiments, mechanical power-transfer connection 22 may alsobe provided between power-conversion device 18 and CVP 26, withpower-transfer connection 28 transmitting power from CVP 26 topower-output connection 32 (e.g., via transmission 30).

In order to control transition between various powered modes of powertrain 12, lock-up device 24 may also be provided. In certainembodiments, as depicted in FIG. 2, device 24 may be located betweenpower-conversion device 18 and CVP 26. As with various other componentsdepicted in FIG. 2, however, various other configurations may bepossible. For example, a lock-up device (e.g., device 24) mayalternatively (or additionally) be arranged between engine 14 andpower-conversion device 18.

Referring also to FIG. 3, an example configuration of series, electricalmulti-mode power train 12 a is provided. As depicted, for example, shaft16 a may extend from engine 14 a to generator 18 a, such that engine 14a may drive generation of electricity by generator 18 a. Electricconduit 36 a may be provided, which may carry electricity from generator18 a to battery assembly 34 a and electric motor 26 a. (As with variousother configurations, various known control apparatuses may be includedfor control of such a power transmission. For example, variouscontrollers and other power electronics (not shown) may be included tocontrol the generation of electricity by generator 18 a, storage andrelease of electrical energy by battery assembly 34 a, powering of motor26 a via conduit 36 a, and so on. Likewise, various actuators,controllers, and so on (not shown) may be provided for control ofvarious components of a lock-up device.)

In certain embodiments, direct mechanical connection 22 a (e.g., arotating shaft or various shafts and mechanical gear sets) may beprovided between engine 14 a and generator 18 a for transmission ofmechanical power from engine 14 a to generator 18 a. Further, in certainembodiments, friction clutch 24 a (or another lock-up device) may beprovided between generator 18 a and motor 26 a. As depicted, forexample, clutch 24 a may be integrated with connection 22 a and a rotorof motor 26 a. In this way, when clutch 24 a is engaged, a directmechanical connection may be established between engine 14 a andconnection 28 a (e.g., another rotating shaft), such that power may beprovided directly from engine 14 a to the remainder of the power train.Further, when clutch 24 a is released, this direct mechanical connectionmay be severed, allowing downstream portions of the power train to bepowered solely by motor 26 a (e.g., as facilitated by electricity fromgenerator 18 a or battery assembly 34 a). In this way, through actuationof clutch 24 a (e.g., as controlled by a transmission control unit (notshown) or other known control devices or methods), power train 12 a maybe transitioned between direct-drive and electric-drive modes. Forexample, clutch 24 a may be released to allow all-electric drive ofvehicle 10 at low or zero speeds, then engaged to transition todirect-drive mode as desired. Further, in certain embodiments, motor 26a may be caused (e.g., via various known control systems (not shown)) tooperate in a reversed direction to also allow all-electric drive of workvehicle 10 for rearward travel. This latter functionality, for example,may allow for elimination of a reversing gear in power train 12 a (e.g.,within power shift transmission 30 a).

The configuration of FIG. 3 (and others) may additionally.(alternatively) allow for capture of power by motor 26 a, or forprovision of supplemental power by motor 26 a. For example, in acoasting or braking operation, motor 26 a may be operated as a generatorin order to convert excess mechanical power to electrical energy forstorage in battery assembly 34 a. Similarly, if power train 12 a isbeing operated in a direct-drive mode, motor 26 a may be utilizedselectively to provide a boost of additional power (e.g., by drawingpower from battery assembly 26 a).

It will be understood that other configurations may be possible,including other configurations with engine 14, power-conversion device18, lock-up device 24, and CVP 26 arranged in series. Referring also toFIG. 4, for example, example power train 12 b is depicted, with a seriesarrangement of engine 14 b, and a hydraulic CVP. For example, mechanicalconnection 16 b (e.g., a rotating shaft, or various shafts and gearsets) may allow for direct mechanical transmission of power from engine14 b to hydraulic pump 18 b and, in certain embodiments, to charge pump20 b. Hydraulic line (or circuit) 36 b may extend from pump 22 b tohydraulic motor 26 b (and, potentially, to hydraulic accumulator 34 b),to facilitate generation of mechanical power by motor 26 b.Power-transfer connection 22 b (e.g., a rotating shaft) may also beprovided, which may provide for mechanical transmission of power fromengine 14 b to lock-up device 24 b. Likewise, connection 28 b mayprovide for transmission of mechanical power from motor 26 b to lock-updevice 24 b.

As depicted, lock-up device 24 b may include friction clutch 40 linkingconnection 22 b to gear 42, and collar clutch 44 (e.g., a dog-collarclutch) linking connection 28 b to gear 42. Gear 42, in turn, may bemeshed with input gears 46 and 52 of power shift transmission (“PST”) 30b. (It will be understood, for this and other examples, that variousother transmission types or configurations may additionally (oralternatively) be employed. Further, in certain embodiments, no PST orother transmission may be provided downstream of lock-up device 24.)Gears 46 and 52, respectively, may be linked via friction clutches 48and 54 to gear shafts 50 and 56, which may include various selectablegears corresponding to various different gear ratios (e.g., gears 62 and64, which may engage with two-way synchronizer clutch 60, and gears 68and 70, which may engage with two-way synchronizer clutch 66). Incertain embodiments, charge pump 20 b may be configured to supplylubrication or cooling fluid to PST 30 b, or other components of powertrain 14 b, as well as to pump 18 b.

In the configuration depicted in FIG. 4, power train 12 b may betransitioned between direct-drive and CVP modes through selectiveactivation of various clutches, and may execute various gear shiftswithin each such mode. For example, with clutch 40 engaged and clutch 44disengaged, engine 14 b may provide mechanical power to gear 42 viadirect mechanical connection (i.e., connections 16 b and 22 b). Variouscombinations of clutches 48, 54, 60, 66, and so on, may then be engagedin order to provide a particular gear ratio between engine 14 b andoutput shaft 32 b. In contrast, with clutch 44 engaged and clutch 40disengaged, the mechanical power-transmission connection between engine14 b and PST 30 b may be severed, and a mechanical power-transmissionconnection established between PST 30 b and motor 26 b. In this way,with motor 26 b operating as driven by pump 18 b (or accumulator 34 b),various combinations of clutches 48, 54, 60, 66, and so on, may beengaged in order to provide a particular gear ratio between motor 26 band output shaft 32 b. In practice, for example, at low or zero speedsfor work vehicle 10, clutch 44 may be engaged in order to provide forhydraulic-only drive of PST 30 b. At a particular vehicle speed, clutch44 may then be disengaged and clutch 40 engaged, in order to provide forefficient, direct-drive powered only by engine 14 b. Further, in certainembodiments, motor 26 b may be driven in a reversed direction, in orderto allow for rearward travel of vehicle 10 in CVP mode.

Various non-series arrangements may also be possible. Referring also toFIG. 5, for example, engine 14 c may directly provide mechanical powerto lock-up device 24 c, hydraulic pump 18 c, and charge pump 20 c viaconnection 16 c (e.g., a rotating shaft, or various shafts and gearsets). Lock-up device 24 c may include friction clutch 80 linked to gear82, which may be meshed with input gears 90 and 94 of PST 30 c.Hydraulic connection 36 c may provide hydraulic power from pump 18 c tohydraulic motor 36 c. Motor 36 c, in turn, may provide mechanical outputvia connection 28 c (e.g., a rotating shaft, or various shafts and gearsets) to friction clutch 84, which may be linked to gear 86. Gears 90and 94, respectively, may be linked via friction clutches 88 and 92 togear shafts 76 and 78, which may include various selectable gears (e.g.,gear 100, configured to engage with synchronizer clutch 98, and gear104, configured to engage with synchronizer clutch 102).

Accordingly, through selective activation of the various clutches, powertrain 12 c may be transitioned between direct-drive and CVP modes, andmay execute various gear shifts within each such mode. For example, withclutch 80 engaged and clutch 84 disengaged, engine 14 c may providepower to gear 82 via a direct mechanical connection. Variouscombinations of clutches 88, 92, 98, 102, and so on, may then be engagedin order to provide a particular gear ratio between engine 14 c andoutput shaft 32 c. With clutch 84 engaged and clutch 80 disengaged, themechanical power-transmission connection between engine 14 c and PST 30c may be severed, and a mechanical power-transmission connectionestablished between PST 30 c and motor 26 c. In this way, with motor 26c operating (e.g., in a forward or a reverse direction, driven by pump18 c), various combinations of clutches 88, 92, 98, 102, and so on, maybe engaged in order to provide a particular gear ratio between motor 26c and output shaft 32 c. In practice, for example, at low or zero speedsfor vehicle 10, clutch 84 may be engaged in order to provide forhydraulic-only drive of PST 30 c. At a particular vehicle speed, clutch84 may then be disengaged and clutch 80 engaged, in order to provide forefficient, direct-drive powered only by engine 14 c.

As depicted in FIG. 5 (and in contrast, for example, to FIG. 4), powertrain 12 c may be configured such that motor 26 c may provide power tooutput shaft 32 c only via a subset of the total gear ratios provided byPST 30 c. This may, for example, reduce system complexity, while stillallowing for a wide range of output speeds at shaft 32 c in CVP mode,due to the potentially large speed range of motor 26 c. (It will beunderstood that similar configurations may also be utilized for otherpower trains 12 and CVPs 26.)

Referring also to FIG. 6, an example tractive-force to wheel-speed curveis provided with respect to a vehicle including power train 12 c(assuming zero wheel slip). At zero and low vehicle speed, for example,power train 12 c may operate in CVP mode, with hydraulic motor 26 cproviding all of the motive power for the vehicle. At a lowest gear ofPST 30 c, accordingly, motor 26 c may allow operation of the vehiclealong curve 120 (with similar operation in reverse (not shown) beingpossible for reverse-direction rotation of motor 26 c). As the vehicleaccelerates, shifts within PST 30 c to other gear ratios may allowcontinued operation of the vehicle along curves 122 and 124, with thevehicle still being driven exclusively by motor 26 c.

At a particular speed (e.g., 12 kph, as indicated by line 138), then, inorder to increase the efficiency of vehicle operation, a transition maybe made to direct-drive mode. For example, clutch 84 may be disengagedto sever the power-transfer connection between motor 26 c and PST 30 c,and clutch 80 may be engaged to provide a direct mechanicalpower-transfer connection between engine 14 c and PST 30 c. The vehiclemay then operate along curves 126, 128, 130, 132, 134 and 136, which mayrepresent, respectively, direct-drive operation in the six gear ratiosprovided by PST 30 c. (It will be understood that the transition to (orfrom) direct-drive mode may occur at other speeds than 12 kph, forvarious operations, vehicles or power trains. Likewise, it will beunderstood that similar curves (not shown) may represent the variousmodes of operation of power trains 12 a or 12 b, or various other powertrains (not shown) that utilize an engine, a lock-up device, and a CVPas generally discussed herein.)

It will be understood that various combinations and variations ofaspects of the examples above may be employed in various alternativeconfigurations without departing from the concepts of this disclosure.In various embodiments, for example, various configurations orcombinations of gear ratios, PST types, CVP types, clutch device types(e.g., wet or dry friction clutches, dog collar clutches, orsynchronizers), power-transfer connection types (e.g., various rotatingshafts, or various geared connections with or without gear reductions),and so on, may be possible. In certain embodiments, for example, byimplementing speed-matching algorithms for a CVP it may be possible toreduce costs and complexity by utilizing collar clutches, rather thanfriction clutches, with respect to power-transfer connections between aparticular CVP 26 and various other power train components. Likewise,various configurations of PSTs 30 may be utilized without departing fromthe spirit of this disclosure, including eight-speed PSTs (e.g., PST 30b), six-speed PSTs (e.g., PST 30 c) or other configurations, including,in certain embodiments, no PST. In certain embodiments, multiplepower-output connections 36 may be provided (e.g., both a PTO connectionand a differential drive shaft from a PST). Further, in certainembodiments and as also noted above, reverse drive powered by a CVP maybe possible through the reverse-direction rotation of the CVP, while inother embodiments a particular reversing gear may be provided. Finally,depiction of a particular CVP (and related components) in an exampleconfiguration as being of a particular type (e.g., an electric motor ora hydraulic motor) is not intended to limit the disclosure to thatparticular type of CVP (and related components).

Continuing, although specific terms such as “generator” and “motor” (andthe like) may be used herein to describe various example configurations,it will be understood that these (and similar) terms may be used torefer generally to an electrical machine that may be capable ofoperating either as a generator or as a motor. For example, electricgenerator 18 a may sometimes operate as an electric motor, and electricmotor 26 a may sometimes operate as a generator. Likewise, it will beunderstood that the actual operating modes of other continuouslyvariable power sources may similarly vary from those explicitlydescribed herein.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the disclosure.As used herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that any use of the terms“comprises” and/or “comprising” in this specification specifies thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

The description of the present disclosure has been presented forpurposes of illustration and description, but is not intended to beexhaustive or limited to the disclosure in the form disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of thedisclosure. Explicitly referenced embodiments herein were chosen anddescribed in order to best explain the principles of the disclosure andtheir practical application, and to enable others of ordinary skill inthe art to understand the disclosure and recognize many alternatives,modifications, and variations on the described example(s). Accordingly,various other implementations are within the scope of the followingclaims.

What is claimed is:
 1. A multi-mode power train for receiving andtransmitting power from an engine, the multi-mode power traincomprising: a power-conversion device in communication with the enginevia a direct mechanical power-transfer connection that extends from theengine to the power-conversion device; a continuously variable powersource in communication with the power-conversion device via anintermediate power-transfer connection; a lock-up device between theengine and at least one of the power-conversion device and thecontinuously variable power source, the lock-up device having first andsecond engagement states; and a power-output connection; wherein, withthe lock-up device in the first engagement state, the power-conversiondevice receives mechanical power from the engine via the directmechanical power-transfer connection and converts the receivedmechanical power to a non-mechanical form, the continuously variablepower source receives the non-mechanical power from the power-conversiondevice via the intermediate power-transfer connection and converts thereceived non-mechanical power to mechanical power, and the continuouslyvariable power source transmits the mechanical power to the power-outputconnection; and wherein, with the lock-up device in the secondengagement state, the engine transmits mechanical power through thelock-up device to the power-output connection.
 2. The multi-mode powertrain of claim 1, wherein the power-conversion device includes ahydraulic pump, and the continuously variable power source includes ahydraulic motor.
 3. The multi-mode power train of claim 1, wherein thepower-conversion device includes an electric generator, and thecontinuously variable power source includes a electric motor.
 4. Themulti-mode power train of claim 1, wherein the engine, thepower-conversion device, the lock-up device, and the continuouslyvariable power source are arranged in series.
 5. The multi-mode powertrain of claim 4, wherein the lock-up device includes a clutch devicebetween the power-conversion device and the continuously variable powersource, the clutch device being integrated with a rotor of thecontinuously variable power source.
 6. The multi-mode power train ofclaim 4, wherein the lock-up device includes a clutch assembly and agear, the clutch assembly and the gear being located between thepower-conversion device and the continuously variable power source;wherein, with the lock-up device in the first engagement state, thecontinuously variable power source transmits mechanical power to thepower-output connection via the clutch assembly and the gear; andwherein, with the lock-up device in the second engagement state, theengine transmits mechanical power to the power-output connection via theclutch assembly and the gear.
 7. The multi-mode power train of claim 1,further comprising: a first clutch device and a first gear, each beingincluded in the lock-up device, the first clutch device and the firstgear being located between the engine and the power-conversion device;and a second clutch device and a second gear, the second clutch deviceand the second gear being located between the continuously variablepower source and the power-output connection; wherein, with the lock-updevice in the first engagement state, and the second clutch engaging thesecond gear, the continuously variable power source transmits mechanicalpower to the power-output connection via the second clutch device andthe second gear; and wherein, with the lock-up device in the secondengagement state, the engine transmits mechanical power to thepower-output connection via the first clutch device and the first gear.8. The multi-mode power train of claim 1, further comprising: an energystorage device in communication with the continuously variable powersource and the power-conversion device; wherein, in a first mode theenergy storage device receives energy for storage from at least one ofthe power-conversion device and the continuously variable power source;and wherein, in a second mode, the energy storage device provides storedenergy from the energy storage device to the continuously variable powersource.
 9. A work vehicle for operation in multiple powered modes, thework vehicle comprising: an engine; a power-conversion device incommunication with the engine via a direct mechanical power-transferconnection that extends from the engine to the power-conversion device;a continuously variable power source in communication with thepower-conversion device via an intermediate power-transfer connection; alock-up device between the engine and at least one of thepower-conversion device and the continuously variable power source, thelock-up device having first and second engagement states; and apower-output connection; wherein, with the lock-up device in the firstengagement state, the power-conversion device receives mechanical powerfrom the engine via the direct mechanical power-transfer connection andconverts the received mechanical power to a non-mechanical form, thecontinuously variable power source receives the non-mechanical powerfrom the power-conversion device via the intermediate power-transferconnection and converts the received non-mechanical power to mechanicalpower, and the continuously variable power source transmits themechanical power to the power-output connection; and wherein, with thelock-up device in the second engagement state, the engine transmitsmechanical power through the lock-up device to the power-outputconnection.
 10. The work vehicle of claim 9, wherein thepower-conversion device includes a hydraulic pump, and the continuouslyvariable power source includes a hydraulic motor.
 11. The work vehicleof claim 9, wherein the power-conversion device includes an electricgenerator, and the continuously variable power source includes aelectric motor.
 12. The work vehicle of claim 9, wherein the engine, thepower-conversion device, the lock-up device, and the continuouslyvariable power source are arranged in series.
 13. The work vehicle ofclaim 9, wherein the lock-up device includes a clutch device between thepower-conversion device and the continuously variable power source, theclutch device being integrated with a rotor of the continuously variablepower source.
 14. The work vehicle of claim 13, wherein the lock-updevice includes a clutch assembly and a gear, the clutch assembly andthe gear being located between the power-conversion device and thecontinuously variable power source; wherein, with the lock-up device inthe first engagement state, the continuously variable power sourcetransmits mechanical power to the power-output connection via the clutchassembly and the gear; and wherein, with the lock-up device in thesecond engagement state, the engine transmits mechanical power to thepower-output connection via the clutch assembly and the gear.
 15. Thework vehicle of claim 9, further comprising: a first clutch device and afirst gear, each being included in the lock-up device, the first clutchdevice and the first gear being located between the engine and thepower-conversion device; and a second clutch device and a second gear,the second clutch device and the second gear being located between thecontinuously variable power source and the power-output connection;wherein, with the lock-up device in the first engagement state, and thesecond clutch engaging the second gear, the continuously variable powersource transmits mechanical power to the power-output connection via thesecond clutch device and the second gear; and wherein, with the lock-updevice in the second engagement state, the engine transmits mechanicalpower to the power-output connection via the first clutch device and thefirst gear.
 16. The work vehicle of claim 9, further comprising: anenergy storage device in communication with the continuously variablepower source and the power-conversion device; wherein, in a first modethe energy storage device receives energy for storage from at least oneof the power-conversion device and the continuously variable powersource; and wherein, in a second mode, the energy storage deviceprovides stored energy from the energy storage device to thecontinuously variable power source.